<?php
Class xxtea {  
    public function encrypt($s, $key) {  
        return base64_encode(self :: xxtea_encrypt($s, $key));  
    }  
    public function decrypt($e, $key) {  
        return self :: xxtea_decrypt(base64_decode($e), $key);  
    }  
    private function long2str($v, $w) {  
        $len = count($v);  
        $n = ($len -1) << 2;  
        if ($w) {  
            $m = $v[$len -1];  
            if (($m < $n -3) || ($m > $n))  
                return false;  
            $n = $m;  
        }  
        $s = array ();  
        for ($i = 0; $i < $len; $i++) {  
            $s[$i] = pack("V", $v[$i]);  
        }  
        if ($w) {  
            return substr(join('', $s), 0, $n);  
        } else {  
            return join('', $s);  
        }  
    }  
    private function str2long($s, $w) {  
        $v = unpack("V*", $s . str_repeat("\0", (4 - strlen($s) % 4) & 3));  
        $v = array_values($v);  
        if ($w) {  
            $v[count($v)] = strlen($s);  
        }  
        return $v;  
    }  
    private function int32($n) {  
        while ($n >= 2147483648)  
            $n -= 4294967296;  
        while ($n <= -2147483649)  
            $n += 4294967296;  
        return (int) $n;  
    }  
    private function xxtea_encrypt($str, $key) {  
        if ($str == "") {  
            return "";  
        }  
        $v = self :: str2long($str, true);  
        $k = self :: str2long($key, false);  
        if (count($k) < 4) {  
            for ($i = count($k); $i < 4; $i++) {  
                $k[$i] = 0;  
            }  
        }  
        $n = count($v) - 1;  
        $z = $v[$n];  
        $y = $v[0];  
        $delta = 0x9E3779B9;  
        $q = floor(6 + 52 / ($n +1));  
        $sum = 0;  
  
        while (0 < $q--) {  
            $sum = self :: int32($sum + $delta);  
            $e = $sum >> 2 & 3;  
            for ($p = 0; $p < $n; $p++) {  
                $y = $v[$p +1];  
                $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
                $z = $v[$p] = self :: int32($v[$p] + $mx);  
            }  
            $y = $v[0];  
            $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
            $z = $v[$n] = self :: int32($v[$n] + $mx);  
        }  
        return self :: long2str($v, false);  
    }  
    private function xxtea_decrypt($str, $key) {  
        if ($str == "") {  
            return "";  
        }  
        $v = self :: str2long($str, false);  
        $k = self :: str2long($key, false);  
        if (count($k) < 4) {  
            for ($i = count($k); $i < 4; $i++) {  
                $k[$i] = 0;  
            }  
        }  
        $n = count($v) - 1;  
  
        $z = $v[$n];  
        $y = $v[0];  
        $delta = 0x9E3779B9;  
        $q = floor(6 + 52 / ($n +1));  
        $sum = self :: int32($q * $delta);  
  
        while ($sum != 0) {  
            $e = $sum >> 2 & 3;  
            for ($p = $n; $p > 0; $p--) {  
                $z = $v[$p -1];  
                $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
                $y = $v[$p] = self :: int32($v[$p] - $mx);  
            }  
            $z = $v[$n];  
            $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
            $y = $v[0] = self :: int32($v[0] - $mx);  
            $sum = self :: int32($sum - $delta);  
        }  
        return self :: long2str($v, true);  
    }  
}  
?>